Display apparatus and method incorporating gaze-based modulation of pixel values

ABSTRACT

A display apparatus including gaze-tracking means, image renderers, liquid-crystal devices including liquid-crystal structure and control circuit, to shift light emanating from given pixel of image renderer to multiple positions, given pixel including colour component; and processor configured to: process gaze-tracking data to determine gaze direction of user&#39;s eye; determine gaze point; display first output image frame; detect if magnitude of difference between first output value and initial second output value of colour component of given pixel in first and second output image frames exceeds first threshold difference; when detected that magnitude of difference exceeds first threshold difference, update initial second output value to sum of first output value and product of distance factor and difference between initial second output and first output values; and display second output image frame.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 16/783,557, titled “DISPLAY APPARATUS AND METHOD OF ENHANCINGAPPARENT RESOLUTION USING LIQUID-CRYSTAL DEVICE” and filed on Feb. 6,2020, which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to display apparatuses incorporatinggaze-based modulation of pixel values. Moreover, the present disclosurerelates to methods of displaying that are implemented via such displayapparatuses.

BACKGROUND

In recent times, immersive technologies such as virtual-reality,augmented-reality, mixed-reality (collectively referred to asextended-reality (XR) technology) are being used to present interactiveXR environments to users in various fields such as entertainment,real-estate, combat training, medical imaging operations, simulators,navigation, and the like. Typically, the users utilize XR devices (forexample, such as an XR headset, a pair of XR glasses, and the like) forexperiencing and interacting with such XR environments. In use, the usergenerally wears an XR device on his/her head.

Conventional XR devices employ various equipment and techniques togenerate and display images that constitute the XR environment. Some XRdevices employ pixel-shifting technology wherein light emanating from agiven pixel of an image renderer (for example, such as a display, aprojector, and the like) is shifted to multiple positions for providingan apparent spatial super-resolution.

However, provision of high spatial resolutions for the images using thepixel-shifting technology has certain problems associated therewith. Forsome XR devices that employ the pixel-shifting technology, the imagerenderers produce colour reproduction artifacts in the images due topoor response time of such image renderers. Generally, the imagerenderers use response time compensation in order to mitigate saidartifacts in the images and to improve perceived colour depth in theimage. However, such response time compensation is performed uniformlyfor an entirety of the images, and thus is well suited to provide only alimited perceived colour depth (namely, a limited colour reproductioncapability) in the images being displayed via the image renderer. Insuch a case, the displayed images are suboptimal in terms of colourreproduction. Moreover, use of the response time compensation using veryhigh setting levels also produces undesirable effects (such as coronaeffects) in the images. For example, leading edges of moving content inthe images may be overshot in the images. Such undesirable effectsdeteriorate immersiveness and realism of the users within the XRenvironments.

Therefore, in light of the foregoing discussion, there exists a need toovercome the aforementioned drawbacks associated with provision ofcolours in high-resolution images in specialized devices.

SUMMARY

The present disclosure seeks to provide a display apparatusincorporating gaze-based modulation of pixel values. The presentdisclosure also seeks to provide a method of displaying that isimplemented via such display apparatus. An aim of the present disclosureis to provide a solution that overcomes at least partially the problemsencountered in prior art.

In one aspect, an embodiment of the present disclosure provides adisplay apparatus comprising:

gaze-tracking means;

an image renderer per eye;

a liquid-crystal device comprising a liquid-crystal structure and acontrol circuit, wherein the liquid-crystal structure is arranged infront of an image-rendering surface of the image renderer, wherein theliquid-crystal structure is to be electrically controlled, via thecontrol circuit, to shift light emanating from a given pixel of theimage renderer to a plurality of positions in a sequential and repeatedmanner, the given pixel comprising at least one colour component; and

at least one processor configured to:

-   -   process gaze-tracking data, collected by the gaze-tracking        means, to determine a gaze direction of a user's eye;    -   determine, based on the gaze direction of the user's eye, a gaze        point on an image plane of the image-rendering surface at which        the user is gazing;    -   display a first output image frame via the image renderer;    -   detect whether or not a magnitude of a difference between a        first output value of a given colour component of the given        pixel in the first output image frame and an initial second        output value of the given colour component of the given pixel in        a second output image frame exceeds a first threshold        difference, wherein the second output image frame is to be        displayed subsequent to the first output image frame;    -   when it is detected that the magnitude of the difference between        the first output value and the initial second output value        exceeds the first threshold difference, update the initial        second output value in the second output image frame to a sum of        the first output value and a product of a distance factor and a        difference between the initial second output value and the first        output value, wherein the distance factor is a function of a        distance of the given pixel from the gaze point on the image        plane; and    -   display the second output image frame via the image renderer.

In another aspect, an embodiment of the present disclosure provides amethod of displaying, via a display apparatus comprising gaze-trackingmeans, an image renderer per eye, and a liquid-crystal device comprisinga liquid-crystal structure and a control circuit, wherein theliquid-crystal structure is arranged in front of an image-renderingsurface of the image renderer, the method comprising:

-   -   electrically controlling the liquid-crystal structure, via the        control circuit, to shift light emanating from a given pixel of        the image renderer to a plurality of positions in a sequential        and repeated manner, the given pixel comprising at least one        colour component;    -   processing gaze-tracking data, collected by the gaze-tracking        means, to determine a gaze direction of a user's eye;    -   determining, based on the gaze direction of the user's eye, a        gaze point on an image plane of the image-rendering surface at        which the user is gazing;    -   displaying a first output image frame via the image renderer;    -   detecting whether or not a magnitude of a difference between a        first output value of a given colour component of the given        pixel in the first output image frame and an initial second        output value of the given colour component of the given pixel in        a second output image frame exceeds a first threshold        difference, wherein the second output image frame is to be        displayed subsequent to the first output image frame;    -   when it is detected that the magnitude of the difference between        the first output value and the initial second output value        exceeds the first threshold difference, updating the initial        second output value in the second output image frame to a sum of        the first output value and a product of a distance factor and a        difference between the initial second output value and the first        output value, wherein the distance factor is a function of a        distance of the given pixel from the gaze point on the image        plane; and    -   displaying the second output image frame via the image renderer.

Embodiments of the present disclosure substantially eliminate or atleast partially address the aforementioned problems in the prior art,and enable presentation of high-quality and high colour-depth visualscenes that are generated by way of modulating pixel values of imageframes based on the gaze direction of user's eye, via the displayapparatus.

Additional aspects, advantages, features and objects of the presentdisclosure would be made apparent from the drawings and the detaileddescription of the illustrative embodiments construed in conjunctionwith the appended claims that follow.

It will be appreciated that features of the present disclosure aresusceptible to being combined in various combinations without departingfrom the scope of the present disclosure as defined by the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The summary above, as well as the following detailed description ofillustrative embodiments, is better understood when read in conjunctionwith the appended drawings. For the purpose of illustrating the presentdisclosure, exemplary constructions of the disclosure are shown in thedrawings. However, the present disclosure is not limited to specificmethods and instrumentalities disclosed herein. Moreover, those skilledin the art will understand that the drawings are not to scale. Whereverpossible, like elements have been indicated by identical numbers.

Embodiments of the present disclosure will now be described, by way ofexample only, with reference to the following diagrams wherein:

FIG. 1 illustrates a block diagram of architecture of a displayapparatus, in accordance with an embodiment of the present disclosure;

FIG. 2 is a schematic illustration of a given pixel of an imagerenderer, in accordance with an embodiment of the present disclosure;

FIG. 3 is a schematic illustration of an image plane of animage-rendering surface at which a user is gazing, in accordance with anembodiment of the present disclosure;

FIGS. 4A and 4B illustrate a plurality of positions to which lightemanating from a given pixel of an image renderer is shifted in asequential and repeated manner, in accordance with different embodimentsof the present disclosure;

FIGS. 4C and 4D illustrate two exemplary shifting sequences in which thelight emanating from the given pixel is to be shifted to four positionsof FIG. 4A, in accordance with different embodiments of the presentdisclosure;

FIGS. 4E and 4F illustrate two exemplary shifting sequences in which thelight emanating from the given pixel is to be shifted to nine positionsof FIG. 4B, in accordance with different embodiments of the presentdisclosure;

FIG. 5A illustrates a given output image frame, while FIG. 5Billustrates a given input image frame, in accordance with an embodimentof the present disclosure; and

FIGS. 6A and 6B illustrate steps of a method of displaying via a displayapparatus, in accordance with an embodiment of the present disclosure.

In the accompanying drawings, an underlined number is employed torepresent an item over which the underlined number is positioned or anitem to which the underlined number is adjacent. A non-underlined numberrelates to an item identified by a line linking the non-underlinednumber to the item. When a number is non-underlined and accompanied byan associated arrow, the non-underlined number is used to identify ageneral item at which the arrow is pointing.

DETAILED DESCRIPTION OF EMBODIMENTS

The following detailed description illustrates embodiments of thepresent disclosure and ways in which they can be implemented. Althoughsome modes of carrying out the present disclosure have been disclosed,those skilled in the art would recognize that other embodiments forcarrying out or practising the present disclosure are also possible.

In one aspect, an embodiment of the present disclosure provides adisplay apparatus comprising:

gaze-tracking means;

an image renderer per eye;

liquid-crystal device comprising a liquid-crystal structure and acontrol circuit, wherein the liquid-crystal structure is arranged infront of an image-rendering surface of the image renderer, wherein theliquid-crystal structure is to be electrically controlled, via thecontrol circuit, to shift light emanating from a given pixel of theimage renderer to a plurality of positions in a sequential and repeatedmanner, the given pixel comprising at least one colour component; and

at least one processor configured to:

-   -   process gaze-tracking data, collected by the gaze-tracking        means, to determine a gaze direction of a user's eye;    -   determine, based on the gaze direction of the user's eye, a gaze        point on an image plane of the image-rendering surface at which        the user is gazing;    -   display a first output image frame via the image renderer;    -   detect whether or not a magnitude of a difference between a        first output value of a given colour component of the given        pixel in the first output image frame and an initial second        output value of the given colour component of the given pixel in        a second output image frame exceeds a first threshold        difference, wherein the second output image frame is to be        displayed subsequent to the first output image frame;    -   when it is detected that the magnitude of the difference between        the first output value and the initial second output value        exceeds the first threshold difference, update the initial        second output value in the second output image frame to a sum of        the first output value and a product of a distance factor and a        difference between the initial second output value and the first        output value, wherein the distance factor is a function of a        distance of the given pixel from the gaze point on the image        plane; and    -   display the second output image frame via the image renderer.

In another aspect, an embodiment of the present disclosure provides amethod of displaying, via a display apparatus comprising gaze-trackingmeans, an image renderer per eye, and a liquid-crystal device comprisinga liquid-crystal structure and a control circuit, wherein theliquid-crystal structure is arranged in front of an image-renderingsurface of the image renderer, the method comprising:

-   -   electrically controlling the liquid-crystal structure, via the        control circuit, to shift light emanating from a given pixel of        the image renderer to a plurality of positions in a sequential        and repeated manner, the given pixel comprising at least one        colour component;    -   processing gaze-tracking data, collected by the gaze-tracking        means, to determine a gaze direction of a user's eye;    -   determining, based on the gaze direction of the user's eye, a        gaze point on an image plane of the image-rendering surface at        which the user is gazing;    -   displaying a first output image frame via the image renderer;    -   detecting whether or not a magnitude of a difference between a        first output value of a given colour component of the given        pixel in the first output image frame and an initial second        output value of the given colour component of the given pixel in        a second output image frame exceeds a first threshold        difference, wherein the second output image frame is to be        displayed subsequent to the first output image frame;    -   when it is detected that the magnitude of the difference between        the first output value and the initial second output value        exceeds the first threshold difference, updating the initial        second output value in the second output image frame to a sum of        the first output value and a product of a distance factor and a        difference between the initial second output value and the first        output value, wherein the distance factor is a function of a        distance of the given pixel from the gaze point on the image        plane; and    -   displaying the second output image frame via the image renderer.

The present disclosure provides the aforementioned display apparatus andthe aforementioned method of displaying. Herein, the magnitude of thedifference between the first output value and the initial second outputvalue of the given colour component of the given pixel is compared withthe first threshold difference, to update the initial second outputvalue in the second output image frame using the distance factor, whensaid magnitude exceeds the first threshold difference. This allows forenhanced colour reproduction capabilities in the image renderer asoutput values of colour components of pixels in the second output imageframe are modulated based on the gaze direction of user's eye forperceiving a high color depth in the second output image frame. Suchmodulation is implemented non-uniformly across pixels of the secondoutput image frame, to provide varied and realistic colour reproductionby the image renderer. Beneficially, this provides immersiveness andrealism within a visual scene of the XR environment. Moreover, thedisplay apparatus and the method employ pixel-shifting technology forproviding an apparent spatial super-resolution that is higher than thedisplay resolution of the image renderer. The method is fast, reliableand can be implemented with ease.

Throughout the present disclosure, the term “display apparatus” refersto a display system that is configured to present an extended-reality(XR) environment to the user when the display apparatus, in operation,is used by the user. Herein, the term “extended-reality” encompassesvirtual reality (VR), augmented reality (AR), mixed reality (MR), andthe like.

In one implementation, the display apparatus is implemented as ahead-mounted device (HMD) and a computer coupled to the HMD. In onecase, the HMD comprises the gaze-tracking means, the image renderer pereye, and the liquid-crystal device, while the computer comprises the atleast one processor. Therefore, computational tasks pertaining topresentation of the XR environment are entirely performed at thecomputer, by the at least one processor. In another case, the HMDcomprises the gaze-tracking means, the image renderer per eye, theliquid-crystal device, and the at least one processor is implemented atboth the HMD and the computer. Therefore, computational tasks pertainingto presentation of the XR environment are performed in a shared mannerat both the HMD and the computer, by the at least one processor. Thecomputer may be coupled to the HMD wirelessly and/or in a wired manner.Examples of the computer include, but are not limited to, a desktopcomputer, a laptop computer, a tablet computer, a workstation, and an XRconsole.

In another implementation, the display apparatus is implemented as anHMD. In such a case, the HMD comprises the gaze-tracking means, theimage renderer per eye, the liquid-crystal device per eye, and the atleast one processor. Therefore, computational tasks pertaining topresentation of the XR environment are entirely performed at the HMD, bythe at least one processor.

It will be appreciated that the HMD is worn by the user on his/her head.The HMD is implemented, for example, as an XR headset, a pair of XRglasses, and the like, that is operable to display a visual scene of theXR environment to the user.

Throughout the present disclosure, the term “gaze-tracking means” refersto a specialized equipment for detecting and/or following gaze of theuser, when the HMD in operation is worn by the user. The gaze-trackingmeans could be implemented as contact lenses with sensors, camerasmonitoring a position of a pupil of the user's eye, and the like. Suchgaze-tracking means are well-known in the art. Notably, thegaze-tracking means is configured to collect the gaze-tracking data. Itwill be appreciated that the gaze-tracking data is collected repeatedlyby the gaze-tracking means throughout a given session of using thedisplay apparatus, as gaze of the user's eyes keeps changing whilsthe/she uses the display apparatus. An up-to-date gaze-tracking dataindicative of the gaze direction of the user allows for producing anup-to-date gaze-contingent XR environment for presenting at the HMD.

Throughout the present disclosure, the term “image renderer” refers toequipment that, in operation, renders (i.e. displays and/or projects)output image frames that are to be shown to the user of the displayapparatus. Herein, the term “output image frame” refers to an imageframe that serves as an output to be displayed by the image renderer.Notably, a plurality of output image frames constitutes the visual sceneof the XR environment. The “image rendering surface” of the imagerenderer refers to a surface of the image renderer from which light ofthe rendered output image frames emanates. It will be appreciated thatthe image renderer has model-specific characteristics pertaining toresponse time.

Optionally, the image renderer is implemented as a display. In thisregard, a given output image frame is displayed at the display. Examplesof the display include, but are not limited to, a Liquid Crystal Display(LCD), a Light-Emitting Diode (LED)-based display, an Organic LED(OLED)-based display, a micro OLED-based display, an Active Matrix OLED(AMOLED)-based display, and a Liquid Crystal on Silicon (LCoS)-baseddisplay. Optionally, the display has a multi-layered structure.Optionally, the image renderer is implemented as a projector. In thisregard, a given output image frame is projected onto a projection screenor directly onto a retina of the user's eyes. Examples of the projectorinclude, but are not limited to, an LCD-based projector, an LED-basedprojector, an OLED-based projector, an LCoS-based projector, a DigitalLight Processing (DLP)-based projector, and a laser projector.

Optionally, the image renderer could be a multi-resolution imagerenderer, or a single-resolution image renderer. Multi-resolution imagerenderers are configured to render output image frames at two or moredisplay resolutions, whereas single-resolution image renderers areconfigured to render output image frames at a single display resolutiononly. Herein, the “display resolution” of the image renderer refers to atotal number of pixels in each dimension of the image renderer, or to apixel density (namely, a number of pixels per unit distance or area) inthe image renderer. The image renderer generally comprises a pluralityof pixels, wherein the plurality of pixels are arranged in a requiredmanner (for example, such as a rectangular two-dimensional grid).

Throughout the present disclosure, the term “colour component” refers toa given colour channel of the given pixel, wherein the given colourchannel is a separately addressable single-color picture element. Insome implementations, the given pixel comprises one colour component(namely, a single colour component). In other implementations, the givenpixel comprises a plurality of colour components (namely, multiplecolour components). The plurality of colour components are arranged in arequired form (for example, such as a one-dimensional array, atwo-dimensional grid, a PenTile® matrix layout, and the like).Optionally, the given pixel comprises 3 colour components. As anexample, the given pixel may comprise a red colour component, a greencolour component, and a blue colour component. As another example, thegiven pixel may comprise a cyan colour component, a magenta colourcomponent, and a yellow colour component. Alternatively, optionally, thegiven pixel comprises 5 colour components. Optionally, in this regard,the 5 sub-pixels comprise two red colour components, two green colourcomponents, and one blue colour component that are arranged in thePenTile® matrix layout. A “colour component” of the given pixel may beunderstood to be a “sub-pixel” of the given pixel.

It will be appreciated that a given colour component of the given pixelis associated with a given output value or an initial given output valuethat is indicative of brightness (namely, an intensity) of the givencolour component of the given pixel. It will be appreciated that thegiven output value or the initial given output value of the given colourcomponent of the given pixel could be represented using any number ofbits, for example, such as 8 bits, 10 bits, 16 bits, 32 bits, and thelike. Optionally, the at least one processor is configured to normalizethe given output value and/or the initial given output value of thegiven colour component of the given pixel to lie in a range of 0 to 1.Optionally, in this regard, the at least one processor employs at leastone normalization function for said normalization. The at least onenormalization function would map the given output value and/or theinitial given output value of the given colour component that lies in afirst range (for example, a range of 0 to 255, or a range of 0 to 1023,or similar) to a corresponding output value that lies in the range of 0to 1. Here in the range of 0 to 1, 0 indicates lowest brightness valueof the given colour component of the given pixel, while 1 indicateshighest brightness value of the given colour component of the givenpixel. For example, the given output value and/or the initial givenoutput value of the given colour component of the given pixel may befrom 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9 up to 0.1, 0.2,0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.

Throughout the present disclosure, the term “liquid-crystal device”refers to a device that enables shifting of light passing therethroughusing a liquid-crystal medium. The liquid-crystal device can beunderstood to steer the light passing therethrough. The liquid-crystalstructure contains the liquid-crystal medium. In operation, the controlcircuit applies electrical signals to control the liquid-crystal mediumcontained within the liquid-crystal structure in a required manner, soas to shift light emanating from the given pixel of the image rendererto the plurality of positions in the sequential and repeated manner.Optionally, the electrical signals applied by the control circuitcontrol an orientation of liquid-crystal molecules of the liquid-crystalmedium. It will be appreciated that the liquid-crystal device isoptimized according to the image renderer. For optimum functioning ofthe display apparatus, the liquid-crystal device is designed accordingto the display resolution of the image renderer. Optionally, the lightemanating from the given pixel of the image renderer is shifted by afraction of the given pixel. In other words, the light emanating fromthe given pixel is shifted by sub-pixel amounts.

Optionally, the liquid-crystal structure comprises a plurality of layersof the liquid-crystal medium that are individually and selectivelyaddressable, wherein a given layer is to be selectively addressed todirect light received thereat from the given pixel or from a previouslayer towards a given direction. Optionally, in this regard, theplurality of layers are collectively addressable to direct the light tothe plurality of positions that lie on the imaginary plane extendingacross two directions in which the light is to be directed.

Optionally, the display apparatus further comprises a collimatorarranged between the image renderer and the liquid-crystal structure.The collimator minimizes spreading of light emanating from each pixel ofthe image renderer, thereby minimizing blending (or overlap) of lightemanating from one pixel of the image renderer with light emanating fromanother pixel of the image renderer. The collimator may be implementedas a perforated plate, a lenticular array, an array of nanotubes(wherein each nanotube of the array collimates light emanating from asingle pixel of the image renderer), a fiber optic plate, or similar.

The at least one processor controls overall operation of the displayapparatus. In particular, the at least one processor is coupled to andcontrols operation of the image renderer and the liquid-crystal device(and specifically, the control circuit of the liquid-crystal device).The at least one processor is also coupled to the gaze-tracking means.The at least one processor may be understood to be a compositor (namely,a processing unit that is configured to perform at least compositingtasks pertaining to presentation of the XR environment). The compositoris a software module taking various inputs (such as the gaze-trackingdata from the gaze-tracking means) and composing (namely, building orgenerating) the output image frames to be displayed via the imagerenderer. The at least one processor generates the sequence of outputimage frames. In an embodiment, the sequence of output image frames isgenerated by a rendering application that is executed by a renderingserver, a processor of the HMD, or the computer coupled to the HMD.

Throughout the present disclosure, the term “gaze direction” refers to adirection in which the user's eye is gazing. The gaze direction may berepresented by a gaze vector. Optionally, when processing thegaze-tracking data, the at least one processor is configured to employat least one of: an image processing algorithm, a feature extractionalgorithm, a data processing algorithm. Other suitable algorithm(s) canalso be employed. It will be appreciated that the gaze direction isdetermined with respect to a perspective of the user's eye. In otherwords, a gaze direction of a left eye of the user and a gaze directionof a right eye of the user are determined with respect to perspectivesof the user's left eye and right eye, respectively.

Throughout the present disclosure, the term “gaze point” refers to apoint on the image plane whereat the gaze direction of the user's eye isdirected (namely, focused), when the user views a given output imageframe. Optionally, the gaze point is determined by mapping the gazedirection of the user's eye to a corresponding location on the imageplane of the image-rendering surface. This gaze point lies in a regionof interest (that is a fixation region) within the given output imageframe. The region of interest is a region of focus of the user's gazewithin the given output image frame. The region of interest is perceivedwith high visual acuity by foveas of the user's eyes, and is resolved toa much greater detail as compared to the remaining region(s) of thegiven output image frame.

It will be appreciated that a gaze point for the left eye and a gazepoint for the right eye are determined based on the gaze direction ofthe left eye and the gaze direction of the right eye, respectively.These gaze points on the image plane could be determined based on anintersection of the gaze directions of the left and right eyes.Throughout the present disclosure, the term “image plane” refers to agiven imaginary plane on which the given output image frame is visibleto the user.

The at least one processor displays the first output image frame via theimage renderer, at a first instant of time. For displaying the firstoutput image frame, each colour component of each pixel in the firstoutput image frame is assigned a corresponding first output value.

A given “output value” of the given colour component of the given pixelin a given output image frame is indicative of brightness of the givencolour component of the given pixel, for displaying the given outputimage frame. An “initial given output value” of the given colourcomponent of the given pixel in the given output image frame isindicative of an initial brightness of the given colour component of thegiven pixel, wherein the given output image frame is to be displayed.The initial given output value may or may not be updated beforedisplaying. Optionally, the at least one processor employs at least onemathematical formula to compute the difference between the first outputvalue and the initial second output value.

The first threshold difference may be either system defined, or userdefined. The first threshold difference may be configurable (namely,adjustable) to suit specific image renderer characteristics and viewingconditions. Optionally, the first threshold difference lies within arange of 0 to 0.5. As an example, the first threshold difference may befrom 0.0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4 or 0.45 up to 0.05,0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5. This range of thefirst threshold difference may be employed when the given output valueand/or the initial given output value of the given colour component ofthe given pixel lies in the range of 0 to 1.

It will be appreciated that the at least one processor is configured tocompare the magnitude of the difference between the first output valueand the initial second output value with the first threshold differenceto detect whether or not the magnitude of the difference exceeds thefirst threshold difference. An absolute value of the magnitude of thedifference would be utilized when comparing the magnitude of thedifference with the first threshold difference. A sign of the differenceis not utilized during such comparing. When it is detected that themagnitude of the difference exceeds the first threshold difference, itindicates that the given pixel has considerable contrast difference, andthat the initial second output value requires updating. Therefore, theinitial second output value is updated to a second output value.Mathematically, in such a case,

Second output value=First output value+(Distance factor*(Initial secondoutput value−First output value))

When applying the distance factor to the difference between the firstoutput value and the initial second output value, a sign of thedifference stays the same (assuming that the distance factor isnon-negative), so when a modulated difference (i.e. distance factor*thedifference between the first output value and the initial second outputvalue) is applied to the first output value, a direction of change inoutput values stays the same.

Optionally, the distance factor decreases with an increase in thedistance. In other words, the distance factor is inversely related tothe distance of the given pixel from the gaze point on the image plane.Optionally, the function is selected, by the at least one processor, ina manner that upon updating the initial second output value using thedistance factor, a difference between the second output value and thefirst output value of the given colour component (that is greater thanor equal to the first threshold difference) is:

-   -   amplified for pixels within the region of interest around the        gaze point in the second output image frame, and    -   attenuated (progressively) for pixels outside the region of        interest in the second output image frame.

In this regard, amplification of the difference between the secondoutput value and the first output value of the given colour componentfor the pixels within the region of interest would provide an effectthat is similar to liquid crystal device overdrive (namely, a responsetime compensation) within the region of interest. The initial secondoutput value would be updated to the second output value whichcorresponds to more change in brightness of the given colour componentfrom the first output value than actually intended. In other words, thesecond output value to which the initial second output value is updated,is greater than an intended second output value for displaying. Then, asresponse time of the liquid crystal device is considerably high (namely,is slow), an actual second output value of the given colour componentmatches the intended second output value of the given colour component.Beneficially, this prevents ghosting effects and increases colorreproduction capabilities in the image renderer at an expense offlickering within the region of interest. As the foveas of the user'seyes are quite insensitive to flicker, this would not cause anydegradation in viewing quality of the XR environment.

Furthermore, attenuation of the difference between the second outputvalue and the first output value of the given colour component for thepixels outside the region of interest would provide an effect that issimilar to a liquid crystal device underdrive in a peripheral regionthat is outside the region of interest. In simpler terms,(high-contrast) differences between the second output value and thefirst output value of pixels in the peripheral region are damped towardstheir average. This prevents flickering in the peripheral region, wherethe user's eye is especially sensitive to the flickering, at the expenseof losing extra apparent resolution provided by shifting the lightemanating from the given pixel of the image renderer to the plurality ofpositions.

It will be appreciated that the selection of the function (of thedistance factor) is done such that outside of the region of interest ofthe user's eye, the at least one processor is able to effectively switchfrom accentuating contrast differences in output values (which is donefor the pixels within the region of interest) to damping them instead,so that there isn't that much flickering in the peripheral region. Inthe display apparatus, colour reproduction in output image frames iswell-adapted to vary according to the gaze location.

Optionally, the distance is measured in degrees as an angular distancebetween the given pixel and the gaze point, wherein the distance factorhas a value that lies in a range of 1-5 for the angular distance thatlies in a range of 0-30 degrees. More optionally, the distance factorhas a value greater than 1 (for example, a value that lies in a range of1-3) for the angular distance that lies in a range of 0-15 degrees. Yetmore optionally, the distance factor has a value greater than 1 (forexample, a value that lies in a range of 1-1.7) for the angular distancethat lies in a range of 0-5 degrees. Herein, the term “angular distance”refers to an angular separation between the given pixel and the gazepoint that is expressed in terms of angles (such as in units of degreesor radians). In an example, the distance factor may be from 1, 1.5, 2,2.5, 3, 3.5, 4 or 4.5 up to 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 for theangular distance that may be from 0, 5, 10, 15, 20 or 25 degrees up to5, 10, 15, 20, 25 or 30 degrees.

Optionally, the distance is measured in pixels, wherein the distancefactor has a value that lies in a range of 1-5 for the distance thatlies in a range of 1 pixel to 1800 pixels. More optionally, the distancefactor has a value greater than 1 (for example, a value that lies in arange of 1-3) for the distance that lies in a range of 1 pixel to 900pixels. Yet more optionally, the distance factor has a value greaterthan 1 (for example, a value that lies in a range of 1-1.7) for thedistance that lies in a range of 1 pixel to 300 pixels. Herein, thepixels may be “physical pixels” of the image renderer, or “logicalpixels” of framebuffer data, and measurement of the distance in eitherof the physical pixels or the logical pixels only affects a scale inwhich the distance factor is used. In an example, the distance factormay be from 1, 1.5, 2, 2.5, 3, 3.5, 4 or 4.5 up to 1.5, 2, 2.5, 3, 3.5,4, 4.5 or 5 for the distance that may be from 1, 100, 200, 300, 400,500, 600, 700, 800, 900, 1000, 1200, 1300, 1400, 1500, 1600 or 1700pixels up to 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1200,1300, 1400, 1500, 1600, 1700 or 1800 pixels.

Optionally, the distance measured in pixels depends on a pixel densityof the image renderer. In an example, the pixel density may be 60 pixelsper degree (PPD) and the angular distance between the given pixel andthe gaze point may be 30 degrees. In such a case, the distance betweenthe given pixel and the gaze point (when measured in pixels) is 1800pixels (calculated as 60*30 pixels=1800 pixels).

As an example, the distance factor may be represented by a functionF(r)=D+smoothstep(A, B, r)*0, wherein

D refers to a minimum value of the function F(r) outside the region ofinterest;

smoothstep(A, B, r) refers to a function that returns a value equal to 0when r is greater than A (or when r>A), and returns a value equal to 1when r is lesser than B (or when r<B);

A refers to an outer diameter (measured in pixels);

B refers to an inner diameter (measured in pixels);

r refers to the distance of the given pixel from the gaze point on theimage plane (measured in pixels); and

-   -   refers to a multiplier term for a value of the function F(r).

Herein, for the given pixel, when r>A (for example, when r may be 700pixels and A may be 600 pixels), a value (which is a minimum value) ofthe function F(r) equals to D, and when r<B (for example, when r may be200 pixels and B may be 300 pixels), a value (which is a maximum value)of the function F(r) equals to O+D. Optionally, the at least oneprocessor employs a Hermite interpolation for values of r that liebetween A and B. An exemplary pseudocode for the distance factor may be:

float smoothstep(float a, float b, float x)

{

float t=saturate((x−a)/(b−a));

return t*t*(3.0−(2.0*t));

}.

It will be appreciated that optionally the second output value (to whichthe initial second output value is updated) lies in a range of 0 to 1.When a sign of the difference between the first output value and theinitial second output value is negative, and resultantly the secondoutput value is a negative value, this negative value is approximated tozero.

In an example, the first output value of the given colour component ofthe given pixel in the first output image frame may be 0.2, the initialsecond output value of the given colour component of the given pixel inthe second output image frame may be 0.5, the first threshold differencemay be 0.15, and the distance factor may be 1.5. Herein, the magnitudeof the difference between the first output value and the initial secondoutput value is 0.3 (calculated as |0.5−0.21|=0.3) which exceeds thefirst threshold difference. In such a case, the initial second outputvalue in the second output image frame is updated to 0.65 (calculated as0.2+(1.5*0.3)=0.65). Therefore, 0.65 is the second output value.

In another example, the first output value of the given colour componentof the given pixel in the first output image frame may be 0.5, theinitial second output value of the given colour component of the givenpixel in the second output image frame may be 0.1, the first thresholddifference may be 0.15, and the distance factor may be 1.5. Herein, themagnitude of the difference between the first output value and theinitial second output value is 0.4 (calculated as 10.1-0.51=0.4) whichexceeds the first threshold difference. In such a case, the initialsecond output value in the second output image frame is updated to 0(calculated as 0.5+(1.5*(−0.4))=−0.1), wherein the negative value isapproximated to zero. Here, 0 is the second output value.

Optionally, the distance factor has a value that lies in the range of0-1. For example, the distance factor may be from 0, 0.1, 0.2, 0.3, 0.4,0.5, 0.6, 0.7, 0.8 or 0.9 up to 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,0.9 or 1.

In an embodiment, different distance factors are to be employed fordifferent colour components of the given pixel. Optionally, in thisregard, the different distance factors are selected based on human eyesensitivity to the different colour components. Typically, human eyesensitivity to the different colour components is different. As anexample, the user's eye is most sensitive a green colour component,lesser sensitive to a red colour component, and least sensitive to ablue colour component. In such an example, three different distancefactors may be optionally employed for the green, red, and blue colourcomponents of the given pixel. In another embodiment, a single distancefactor is employed for different colour components of the given pixel.

The at least one processor displays the second output image frame viathe image renderer, at a second instant of time. For displaying thesecond output image frame, each colour component of each pixel in thesecond output image frame is assigned a corresponding second outputvalue.

Whilst displaying a given output image frame, the liquid-crystalstructure is controlled by the at least one processor (via a requisitedrive signal) to shift light through itself according to a requisiteshifting sequence and a number of positions in the plurality ofpositions. The shift in the light emanating from the given pixel of theimage renderer to the plurality of positions causes the resolution ofoutput image frames to appear higher than the display resolution of theimage renderer. Given that the light emanating from the given pixel isshifted to X positions in a sequential and repeated manner, X outputimage frames (that are displayed via the image renderer) would be shownto the user at their corresponding X positions, X being equal to orgreater than 2. The user is unable to discern the shift of the givenpixel and perceives a unified view of the X output image frames having aresolution that is higher than the display resolution. As an example,the light emanating from the given pixel of the image renderer may beshifted to four positions in the sequential and repeated manner. Thiscauses the resolution of the output image frames to appear four timeshigher than the display resolution.

Optionally, the at least one processor is configured to determine outputvalues of colour components of the given pixel in a plurality of outputimage frames, based on a shifting sequence in which the light emanatingfrom the given pixel is to be shifted to the plurality of positions. Theoutput values of colour components of the given pixel depend on aposition to which the given pixel is to be shifted during display of theplurality of output image frames (namely the position at which the givenpixel will be made visible to the user). Therefore, the at least oneprocessor is required to know the shifting sequence in which the lightemanating from the given pixel is to be shifted to the plurality ofpositions. In simple terms, the same physical pixel of the imagerenderer is utilized to display X different ‘virtual pixels’ in Xconsecutive output image frames, based on the shifting sequence in whichlight emanating from the given pixel is to be shifted to X positions, Xbeing equal to or greater than 2. It will be appreciated that the outputvalues of colour components of the given pixel collectively define apixel value of the given pixel.

Optionally, when it is detected that the magnitude of the differencebetween the first output value and the initial second output value doesnot exceed the first threshold difference, the at least one processordoes not update the initial second output value in the second outputimage frame. This situation occurs when said difference is equal to orlesser than the first threshold difference. In such a case, the initialsecond output value of the given colour component of the given pixel isutilized (without updating) as the second output value in the secondoutput image frame.

Optionally, the at least one processor is configured to:

-   -   quantize the initial second output value of the given colour        component of the given pixel by dividing the initial second        output value with a quantization factor, to generate an        intermediate second output value of the given colour component;        and    -   add a given noise-signal value to the intermediate second output        value to generate a given output value of the given colour        component.

In this regard, the initial second output value to be quantized may beun-updated or updated, as described previously. It will be appreciatedthat in order to increase perceived colour depths and/or colourreproduction capabilities in the image renderer, the at least oneprocessor optionally performs dithering for each colour component ofpixels within output image frames. Said dithering typically provides anaccurate colour reproduction at an expense of temporal resolution, butas the display apparatus already employs pixel-shifting technology thatimproves spatial resolution at the expense of temporal resolution, saiddithering essentially becomes computationally free for use. The term“dithering” refers to a process of intentionally adding the givennoise-signal value (that is temporally dynamic) to the intermediatevalue of the given colour component to generate the given value of thegiven colour component so that a quantization error is randomized.

It will also be appreciated that pixel value calculations are performedat a high accuracy than the image renderer itself can display. Forexample, the image renderer may be able to display 256 levels ofbrightness for each color component of the given pixel by using 8 bitsper color component of the given pixel for said calculations, but thecalculations could be performed using 32-bit floating point numbers percolour component of the given pixel, thereby increasing perceived colourdepths and/or colour reproduction capabilities.

Optionally, the initial second output value of the given colourcomponent is represented using 10 bits, and the intermediate secondoutput value of the given colour component is represented using 8 bits.Then, the initial second output value of the given colour component ofthe given pixel lies in a range of 0 to 1023, and the intermediatesecond output value of the given colour component of the given pixellies in a range of 0 to 255. In an example, the initial second outputvalue of the given colour component may be 824, the quantization factormay be equal to 4, and corresponding generated intermediate secondoutput value of the given colour component may be 206.

The term “quantization factor” refers to a factor that is used forquantizing (namely, compressing in a lossy manner) a range of initialsecond output values of the given colour component into a singleintermediate second output value of the given colour component.Referring to the above example, the quantization factor of 4 indicatesthat a range of four initial second output values can be quantized togenerate one intermediate second output value.

It will be appreciated that for a given range of the initial secondoutput values of the given colour component that map to a sameintermediate second output value of the given colour component, aneffect of adding the noise-signal value would be that initial secondoutput values that are on a higher side of said range are more likely tomap to an intermediate second output value one quantization step higherthan in a case of non-dithered mapping, and that initial second outputvalues that are on a lower side of said range are more likely to map toan intermediate second output value one quantization step lower than inthe case of non-dithered mapping, hence dithering is provided. As thenoise-signal value is different for different pixels and/or differentimage frames, due to the dithering, the user will perceive a high colordepth in the output image frames. In the case of non-dithered mapping,the initial second output values (for example, lying in the range of0-1023) would simply be quantized to generate intermediate second outputvalues (for example, lying in the range of 0-255) that would have beensubsequently rounded off. But in such a case, colour depth perceptionwould not have been improved. It will also be appreciated that after itsgeneration, the given value of the given colour component is optionallyrounded off, such as to a nearest integer value.

Optionally, the at least one processor is configured to determine thegiven noise-signal value using a noise generator function or a noisetexture lookup, based on pixel coordinates of the given pixel. The term“noise-signal value” refers to a value that represents an amplitude ofnoise.

Optionally, a given noise texture is a two-dimensional (2D) noisetexture. Alternatively, optionally, a given noise texture is athree-dimensional (3D) noise texture. Herein, the term “two-dimensionalnoise texture” refers to a noise texture having variation of noise in a2D space, and the term “three-dimensional noise texture” refers to anoise texture having variation of noise in a 3D space. It will beappreciated that different coordinates in the 2D space/3D spacerepresent different noise-signal values. Optionally, the 2D noisetexture and the 3D noise texture are smooth and continuous noise fieldsin the 2D space and the 3D space, respectively. Beneficially, employingthe smooth and continuous noise fields (namely, spatially and temporallyvarying noise fields) enable in preventing formation of undesirablevirtual patterns (such as Modified Uniformly Redundant Array (MURA)patterns) in output image frames. When the 3D noise texture is a smoothand continuous noise field, the at least one processor is optionallyconfigured to obtain a plurality of 2D noise textures from the 3D noisetexture. This is attributed to the fact that an interpolation betweentwo adjacent 2D noise-texture slices is feasible as there are no sharp(namely, abrupt) changes in the noise-signal values in individual 2Dnoise textures of the 3D noise texture. In an example implementation,there could be 16 slices of the 2D noise texture in the 3D noisetexture. Optionally, the 3D noise texture is generated using a 3D noisegenerator function.

Optionally, the at least one processor is configured to: obtaininformation indicative of a head pose of a user; and select the 2D noisetexture from amongst a plurality of 2D noise textures based on the headpose of the user. Optionally, the at least one processor is configuredto obtain the information indicative of the head pose of the user frompose-tracking means. The pose-tracking means could be implemented as aninternal component of the HMD, as a tracking system external to the HMD,or as a combination thereof. The pose-tracking means could beimplemented as at least one of: an optics-based tracking system (whichutilizes, for example, infrared beacons and detectors, infrared cameras,visible-light cameras, detectable objects and detectors, and the like),an acoustics-based tracking system, a radio-based tracking system, amagnetism-based tracking system, an accelerometer, a gyroscope, anInertial Measurement Unit (IMU), a Timing and Inertial Measurement Unit(TIMU).

In an embodiment, the noise generator function is a value noisefunction. In another embodiment, the noise generator function is agradient noise function. Examples of the noise generator function mayinclude, but are not limited to, a blue noise function, a white noisefunction, a Perlin noise function, a Gaussian noise function, a simplexnoise function, a diamond-square algorithm, a simplified value noisefunction based on prime number offsets, a random noise generatorfunction, an algorithmic noise generator function. Optionally, when thenoise generator function is the random noise generator function, the atleast one processor is configured to employ the random noise generatorfunction to select a random number as the given noise-signal value. Therandom number may, for example, lie in a range of: −0.3 to 0.3, −0.5 to0.5, −0.7 to 0.7 or similar. It will be appreciated that optionally thegiven noise-signal value is adjusted, by the at least one processor,based on a user feedback.

Optionally, when determining the given noise-signal value, the at leastone processor is configured to map the pixel coordinates of the givenpixel to a corresponding noise-signal value generated using the noisegenerator function or the noise texture lookup. Noise-signal values forpixels having different pixel coordinates may be different. Optionally,lookup table(s) may be employed for determining pixelcoordinate-specific noise-signal values for various pixels. Optionally,the at least one processor is configured to determine the givennoise-signal value using the noise generator function or the noisetexture lookup, based also on time, when the noise generator function orthe noise texture is time-variant. It will be appreciated that noisegeneration methods other than the noise generator function or the noisetexture lookup can also be employed in the display apparatus.

Optionally, the at least one processor is configured to process an inputsequence of input image frames to generate an output sequence of outputimage frames, wherein a number of input image frames in the inputsequence and a number of output image frames in the output sequence areequal to a number of positions in the plurality of positions, andwherein a number of pixels in a given input image frame is equal to aproduct of a number of pixels in a given output image frame and thenumber of positions,

wherein, when generating the output image frames, the at least oneprocessor is configured to:

-   -   determine, based on the gaze point on the image plane, at least        a first input region and a second input region within each input        image frame, wherein the first input region includes and        surrounds the gaze point, and the second input region surrounds        the first input region;    -   divide each input image frame into a plurality of groups of        neighbouring input pixels based on a shifting sequence in which        the light emanating from the given pixel is to be shifted to the        plurality of positions, wherein a number of input pixels in a        given group of neighbouring input pixels is equal to the number        of positions in the plurality of positions; and    -   generate, from an N^(th) input pixel in a given group of        neighbouring input pixels within a first input region of an        N^(th) input image frame in the input sequence, a corresponding        pixel for a first output region of an N^(th) output image frame        in the output sequence.

Throughout the present disclosure, the term “input image frame” refersto an image frame that serves as an input for generating a correspondingoutput image frame. The sequence of input image frames is not shown tothe user, whereas the sequence of output image frames is shown to theuser. The number of pixels in the given input image frame is greaterthan the number of pixels in the given output image frame, as for eachpixel of the given output image frame, the given input image frameincludes multiple pixels (equivalent to the number of positions in theplurality of positions) that are to be utilized one by one forgenerating the given pixel in multiple output image frames. Framebufferdata for generating the output image frames is readily available and isequal to N times the display resolution of the image renderer, N beingthe number of positions in the plurality of positions). In other words,the framebuffer data (that includes input values of colour components ofall input pixels in input image frames) has a logical resolution that isequal to N times the display resolution of the image renderer. At anygiven time, only 1/N input pixels of the given input image frame areutilized to generate corresponding pixels of the given output imageframe.

Optionally, a shape of the first input region is one of: a polygon, acircle, an ellipse, a freeform shape. It will be appreciated that theremay optionally be determined additional input regions (such as a thirdinput region, a fourth input region, and so forth) within each inputimage frame. Such additional input regions may optionally lie betweenthe first input region and the second input region.

Throughout the present disclosure, the term “shifting sequence” refersto a time-based order in which the light emanating from the given pixelis to be shifted to the plurality of positions. The shifting sequencemay be a raster scanning sequence, a random sequence, a Halton sequence(for example, 256 or 1024 first locations of Halton (2, 3)), or similar.It will be appreciated that various shifting sequences may be feasiblefor shifting the light emanating from the given pixel to the pluralityof positions.

It will be appreciated that a shape of the area of the image rendererthat includes the plurality of positions could be polygonal (forexample, rectangular, square, hexagonal, and the like), circular,elliptical, freeform, and the like. It will also be appreciated thatsaid area is defined based on a sub-pixel scheme and spacing between thepixels and/or between the sub-pixels. Optionally, the plurality ofpositions of the given pixel form: a polygonal arrangement, a circulararrangement, an elliptical arrangement, a freeform arrangement.Optionally, when dividing each input image frame into the plurality ofgroups of neighbouring input pixels, the input pixels to be included inthe given group are determined based on the shifting sequence.

In an example, there may be four positions P1, P2, P3, and P4 (arrangedas a 2*2 grid) in the plurality of positions. Then, the number of inputimage frames in the input sequence and the number of output image frameswould be equal to four. Let us consider, for example, that the number ofpixels in each output frame is equal to 16 and therefore, the number ofpixels in each input frame would be 64. Herein, each input image framewould be divided into 16 groups of neighbouring input pixels, whereinthe number of input pixels in each of the 16 groups is equal to fourpixels. Based on the gaze point on the image plane, the first inputregion of the N^(th) input image frame may be identified as a top-leftregion of the N^(th) input image frame, while the second input region ofthe N^(th) input image frame may be identified as a remaining region ofthe N^(th) input image frame. For example, the first input regionincludes two groups of neighbouring input pixels from amongst the 16groups, whereas the second input region includes 14 groups ofneighbouring input pixels from amongst the 16 groups. Let us considerthat 1^(st), 2^(nd), 3^(rd) and 4^(th) input pixels in a given group ofneighbouring pixels within a first input region of a given input imageframe are represented as:

aN|bN

---|---

dN|cN

Herein, the at least one processor may be configured to generate: from a1^(st) input pixel (a1) in the given group of a 1^(st) input imageframe, a corresponding pixel (that is to be shifted to the position P1)for a first output region of a 1^(st) output image frame; from a 2^(nd)input pixel (b2) in the given group of a 2^(nd) input image frame, acorresponding pixel (that is to be shifted to the position P2) for afirst output region of a 2^(nd) output image frame; from a 3^(rd) inputpixel (c3) in the given group of a 3^(rd) input image frame, acorresponding pixel (that is to be shifted to the position P3) for afirst output region of a 3^(rd) output image frame; and from a 4^(th)input pixel (d4) in the given group of a 4^(th) input image frame, acorresponding pixel (that is to be shifted to the position P4) for afirst output region of a 4^(th) output image frame. It will beappreciated that the above example is for illustration purposes only,and various other examples with different values of the number ofpositions in the plurality of positions, different values of the numberof pixels in the given output image frame, different gaze points, andthe like, are also feasible.

Optionally, when generating the output image frames, the at least oneprocessor is configured to combine input pixels in a given group ofneighbouring input pixels within a second input region of an M^(th)input image frame in the input sequence to generate a correspondingpixel for a second output region of an M^(th) output image frame in theoutput sequence. Herein, “combining” refers to an image processingoperation wherein pixel values of the input pixels in the given group ofneighbouring input pixels within the second input region of the M^(th)input image frame are combined to yield a single resultant pixel value,the single resultant pixel value being associated with a singlecorresponding pixel for a second output region of the M^(th) outputimage frame. Therefore, combining operation incorporates visualinformation associated with the input pixels in the given group ofneighbouring input pixels into the corresponding pixel for the secondoutput region of the M^(th) output image frame. Upon such combination,the generated corresponding pixel in the second output region of theM^(th) output image frame is larger in size as compared to a size of aninput pixel in the second region of the M^(th) input image frame. As aresult of the combining operation, angular resolution of the secondoutput region of the M^(th) output image frame is lower than angularresolution of the second input region of the M^(th) input image frame.

Optionally, when combining the input pixels in the given group ofneighbouring input pixels within a second input region of the M^(th)input image frame in the input sequence to generate the correspondingpixel for the second output region of the M^(th) output image frame inthe output sequence, the at least one processor is configured to employat least one of: pixel binning, averaging, weighted averaging,non-linear median filtering, minimum-maximum filtering, interpolation,image scaling (namely, image resizing).

Optionally, the output sequence of output image frames is displayed in amanner that second output regions of the output image frames appear tohave a higher frame rate than first output regions of the output imageframes. A temporal resolution of the second output regions is higherthan a temporal resolution of the first output regions of the outputimage frames. The apparent frame rate (namely, the temporal resolution)of the second output regions of the output image frames is high (forexample, such as 90 frames per second (FPS), 100 FPS, 120 FPS, 180 FPS,240 FPS, and the like). Resultantly, no flicker or jerk is noticed bythe user in the second output regions of the output image frames.Moreover, when the sequence of output image frames is displayed, theuser perceives higher visual detail in the first output regions of theoutput image frames as compared to the second output regions of theoutput image frames.

Optionally, when generating a given output image frame, the at least oneprocessor is configured to generate output values for the first outputregion and the second output region in a manner that an angularresolution of the first output region is higher than an angularresolution of the second output region. Herein, the term “angularresolution” of a given output region of a given image frame refers to anumber of pixels per degree (also referred to as points per degree(PPD)) in the given region. In other words, angular resolution of thegiven output region of the given image frame refers to a pixel densityin the given output region. Notably, a high angular resolution of thegiven output region is indicative of a high visual detail of the givenoutput region. The given output image frame optionally has a variableangular resolution. The variable angular resolution of the sequence ofoutput image frames emulates and approximates human-eye resolution andhuman-eye foveation properties, without requiring use of expensivehigh-resolution image renderers and additional optical components. Theangular resolution of the first output region optionally approximatessuper-resolution, the super-resolution being provided only in the firstoutput region as foveas of the user's eyes are quite insensitive toflicker that is introduced upon provision of the super-resolution. Inthe second output region, the super-resolution is not provided sinceremaining portions of the retinas of the user's eyes are quite sensitiveto flicker.

It will be appreciated that the color reproduction capabilities aresignificantly improved when generating the output image frames based onthe gaze direction of users eye. This is attributed to the fact thatcolour reproduction for different output regions of the output imageframes, such as the first output region and the second output region, isperformed differently in an optimized manner, using the distance factor.

Optionally, the first output value of the given colour component of thegiven pixel in the first output image frame is generated from an inputvalue of the given colour component of a first input pixel in a givengroup of neighbouring input pixels in a first input image frame, whereinthe at least one processor is configured to:

-   -   detect whether or not an initial difference between the input        value of the given colour component of the first input pixel and        an input value of the given colour component of a second input        pixel in the given group of neighbouring input pixels in the        first input image frame lies within a second threshold value        from the difference between the first output value and the        initial second output value; and    -   when it is detected that the initial difference lies within the        second threshold value from the difference between the first        output value and the initial second output value, employ the        initial second output value of the given colour component of the        given pixel in the second output image frame, irrespective of        whether or not the magnitude of the difference between the first        output value and the initial second output value exceeds the        first threshold difference.

As an example, let us consider that 1^(st), 2^(nd), 3^(rd) and 4^(th)input pixels in a given group of neighbouring pixels in a given inputimage frame are represented as:

aN|bN

---|---

dN|cN.

Then, the initial difference between the input value of the given colourcomponent of input pixel a1 and the input value of the given colourcomponent of input pixel b1 is compared with the difference between thefirst output value and the initial second output value may be expressedas a1−b2. In other words, a contrast difference between a1 and b2 iscompared to a contrast difference between a1 and b1 (to determine ifthese are still the same pixel colors as they were in last image frame).It will be appreciated that during said comparison a sign of the initialdifference (i.e. a1−b1) is considered to be significant as the at leastone processor is configured to detect whether or not a same differenceexists between a previous input image frame and a current input imageframe.

The second threshold allows for some leeway when either of colors of thefirst input pixel or the second input pixel change subtly (due tochanges in lighting conditions, or similar) across image frames. Thesecond threshold value may be either system defined, or user defined.The second threshold value may be configurable (namely, adjustable).Optionally, the second threshold value lies within a range of −0.1 to0.1. As an example, the second threshold value may be from −0.1, −0.09,−0.08, −0.07, −0.06, −0.05, −0.04, −0.03, −0.02, −0.01, 0, 0.01, 0.02,0.03, 0.04, 0.05, 0.06, 0.07, 0.08 or 0.09 up to −0.09, −0.08, −0.07,−0.06, −0.05, −0.04, −0.03, −0.02, −0.01, 0, 0.01, 0.02, 0.03, 0.04,0.05, 0.06, 0.07, 0.08, 0.09 or 0.1. Other ranges of the secondthreshold value are also feasible.

In case of a stationary object (having static edges) being representedin consecutive output image frames, the initial difference lies withinthe second threshold value from the difference between the first outputvalue and the initial second output value. In such a case, the at leastone processor would rely on a built-in liquid crystal device overdrivein order to prevent halo effects such as around lighting areas in theoutput image frames, and employ (without updating) the initial secondoutput value of the given colour component of the given pixel in thesecond output image frame. Alternatively, in case of a moving objectbeing represented in the consecutive output image frames, the initialdifference is considerable and does not lie within the second thresholdvalue from the difference between the first output value and the initialsecond output value. In such a case, the at least one processor wouldnot rely on the built-in liquid crystal device overdrive for propercolour reproduction, and the at least one processor will employ anupdated initial second output value of the given colour component of thegiven pixel in the second output image frame in order to provide theeffect that is similar to the liquid crystal device overdrive. Thisprevents occurrence of ghosting artifacts when the moving object isbeing displayed. The apparent increase to be provided in the resolutionof the output image frames also enables in better distinguishing betweenthe stationary object and the moving object, and better adapting forcolour reproduction accordingly.

Optionally, when it is detected that the initial difference does not liewithin the second threshold value from the difference between the firstoutput value and the initial second output value, the at least oneprocessor is configured to update the initial second output value of thegiven colour component of the given pixel when the magnitude of thedifference between the first output value and the initial second outputvalue exceeds the first threshold difference.

The present disclosure also relates to the method as described above.Various embodiments and variants disclosed above, with respect to theaforementioned first aspect, apply mutatis mutandis to the method.

Optionally, in the method, the distance factor decreases with anincrease in the distance.

Optionally, in the method, the distance is measured in degrees as anangular distance between the given pixel and the gaze point, wherein thedistance factor has a value that lies in a range of 1-5 for the angulardistance that lies in a range of 0-30 degrees.

Optionally, in the method, the distance is measured in pixels, whereinthe distance factor has a value that lies in a range of 1-5 for thedistance that lies in a range of 1-1800 pixels.

Optionally, in the method, different distance factors are employed fordifferent colour components of the given pixel.

Optionally, the method further comprises:

-   -   quantizing the initial second output value of the given colour        component of the given pixel by dividing the initial second        output value with a quantization factor, to generate an        intermediate second output value of the given colour component;        and    -   adding a given noise-signal value to the intermediate second        output value to generate a given output value of the given        colour component.

Optionally, the method further comprises determining the givennoise-signal value using a noise generator function or a noise texturelookup, based on pixel coordinates of the given pixel.

Optionally, the method further comprises processing an input sequence ofinput image frames to generate an output sequence of output imageframes, wherein a number of input image frames in the input sequence anda number of output image frames in the output sequence are equal to anumber of positions in the plurality of positions, and wherein a numberof pixels in a given input image frame is equal to a product of a numberof pixels in a given output image frame and the number of positions,

wherein the step of generating the output image frames comprises:

-   -   determining, based on the gaze point on the image plane, at        least a first input region and a second input region within each        input image frame, wherein the first input region includes and        surrounds the gaze point, and the second input region surrounds        the first input region;    -   dividing each input image frame into a plurality of groups of        neighbouring input pixels based on a shifting sequence in which        the light emanating from the given pixel is to be shifted to the        plurality of positions, wherein a number of input pixels in a        given group of neighbouring input pixels is equal to the number        of positions in the plurality of positions; and    -   generating, from an N^(th) input pixel in a given group of        neighbouring input pixels within a first input region of an        N^(th) input image frame in the input sequence, a corresponding        pixel for a first output region of an N^(th) output image frame        in the output sequence.

Optionally, in the method, the step of generating the output imageframes further comprises combining input pixels in a given group ofneighbouring input pixels within a second input region of an M^(th)input image frame in the input sequence to generate a correspondingpixel for a second output region of an M^(th) output image frame in theoutput sequence.

Optionally, when the first output value of the given colour component ofthe given pixel in the first output image frame is generated from aninput value of the given colour component of a first input pixel in agiven group of neighbouring input pixels in a first input image frame,the method further comprises:

detecting whether or not an initial difference between the input valueof the given colour component of the first input pixel and an inputvalue of the given colour component of a second input pixel in the givengroup of neighbouring input pixels in the first input image frame lieswithin a second threshold value from the difference between the firstoutput value and the initial second output value; and when it isdetected that the initial difference lies within the second thresholdvalue from the difference between the first output value and the initialsecond output value, employing the initial second output value of thegiven colour component of the given pixel in the second output imageframe, irrespective of whether or not the magnitude of the differencebetween the first output value and the initial second output valueexceeds the first threshold difference.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, illustrated is a block diagram of architecture of adisplay apparatus 100, in accordance with an embodiment of the presentdisclosure. The display apparatus 100 comprises gaze-tracking means 102,an image renderer per eye (depicted as an image renderer 104 for a firsteye and an image renderer 106 for a second eye), a liquid-crystal deviceper eye (depicted as a liquid-crystal device 108 for the first eye and aliquid-crystal device 110 for the second eye), and at least oneprocessor (depicted as a processor 112). The liquid crystal devices 108and 110 comprise liquid-crystal structures 114 and 116 and controlcircuits 118 and 120, respectively. The liquid-crystal structures 114and 116 are arranged in front of image-rendering surfaces of the imagerenderers 104 and 106, respectively, wherein the liquid-crystalstructures 114 and 116 are electrically controlled, via the controlcircuits 118 and 120, respectively.

It may be understood by a person skilled in the art that the FIG. 1includes simplified architecture of display apparatus 100 for sake ofclarity, which should not unduly limit the scope of the claims herein.The person skilled in the art will recognize many variations,alternatives, and modifications of embodiments of the presentdisclosure.

Referring to FIG. 2, illustrated is a schematic illustration of a givenpixel 200 of an image renderer, in accordance with an embodiment of thepresent disclosure. The given pixel 200 comprises three colourcomponents (notably, a red colour component depicted as ‘R’, a greencolour component depicted as ‘G’, and a blue colour component depictedas ‘B’) that are arranged in a one-dimensional array.

It may be understood by a person skilled in the art that the FIG. 2includes simplified illustration of a given pixel 200 of the imagerenderer for sake of clarity, which should not unduly limit the scope ofthe claims herein. The person skilled in the art will recognize manyvariations, alternatives, and modifications of embodiments of thepresent disclosure. In an example, the given pixel may comprise only onecolour component. In another example, the given pixel may comprise fivecolour components (such as two red colour components, two green colourcomponents, and one blue colour component) that are arranged in aPenTile® matrix layout.

Referring to FIG. 3, illustrated is a schematic illustration of an imageplane 300 of an image-rendering surface at which a user is gazing, inaccordance with an embodiment of the present disclosure. Herein, a gazepoint (depicted as ‘X’) lies, for example, at a centre of the imageplane 300. A distance factor for a given pixel (depicted as ‘Y’) is afunction of a distance (depicted as ‘r’) of the given pixel Y from thegaze point X on the image plane 300.

Referring to FIGS. 4A and 4B, illustrated are positions to which lightemanating from a given pixel of an image renderer is shifted in asequential and repeated manner, in accordance with different embodimentsof the present disclosure. In FIGS. 4A and 4B, these positions arerepresented as blackened circles, and a square outline is depictedmerely to show an area where the shifting takes place. Such an area canalso have any other suitable shape.

In FIG. 4A, the light emanating from the given pixel is shifted to fourpositions P1, P2, P3, and P4. These four positions P1-P4 form a 2×2array. In FIG. 4B, the light emanating from the given pixel is shiftedto nine positions P1, P2, P3, P4, P5, P6, P7, P8, and P9. These ninepositions P1-P9 form a 3×3 array.

It may be understood by a person skilled in the art that the FIGS. 4Aand 4B include exemplary positions to which light-shifting takes placefor sake of clarity, which should not unduly limit the scope of theclaims herein. The person skilled in the art will recognize manyvariations, alternatives, and modifications of embodiments of thepresent disclosure. In an example, the light emanating from the givenpixel may be shifted to 12 positions. These 12 positions may form a 4×3array. In another example, the light emanating from the given pixel maybe shifted to 9 positions. These 9 positions may form a centeredcircular arrangement.

Referring to FIGS. 4C and 4D, illustrated are two exemplary shiftingsequences in which the light emanating from the given pixel is to beshifted to four positions P1-P4 of FIG. 4A, in accordance with differentembodiments of the present disclosure. An order in which the positionsare to be shifted sequentially is indicated by way of arrows. In FIG.4C, the shifting sequence is: P1, P2, P3, P4. In FIG. 4D, the shiftingsequence is: P1, P2, P4, P3.

Referring FIGS. 4E and 4F, illustrated are two exemplary shiftingsequences in which the light emanating from the given pixel is to beshifted to nine positions of FIG. 4B, in accordance with differentembodiments of the present disclosure. An order in which the positionsare to be shifted sequentially is indicated by way of arrows. In FIG.4E, the shifting sequence is: P1, P2, P3, P4, P5, P6, P7, P8, P9. InFIG. 4F, the shifting sequence is: P1, P2, P3, P6, P9, P8, P7, P4, P5.

Referring to FIGS. 5A and 5B, FIG. 5A illustrates a given output imageframe 502, while FIG. 5B illustrates a given input image frame 504, inaccordance with an embodiment of the present disclosure. The “givenoutput image frame” and “given input image frame” may be understood tobe an N^(th) output image frame and an N^(th) input image frame,respectively.

In FIG. 5A, the given output image frame 502 has 12 pixels Z1, Z2, Z3,Z4, Z5, Z6, Z7, Z8, Z9, Z10, Z11, and Z12. Herein, the given outputimage frame 502 comprises a first output region 502A, and a secondoutput region 502B, wherein the pixels Z6 and Z7 belong to the firstoutput region 502A, while the pixels Z1, Z2, Z3, Z4, Z5, Z8, Z9, Z10,Z11, and Z12 belong to the second output region 502B.

In FIG. 5B, a gaze point ‘X’ lies, for example, at a centre of an imageplane of an image-rendering surface at which a user is gazing. The giveninput image frame 504 comprises a first input region 504A, and a secondinput region 504B, wherein the first input region 504A includes andsurrounds the gaze point X, and the second input region 504B surroundsthe first input region 504A.

A number of pixels in the given input image frame 504 is equal to 108(as 12*9=108 (a product of a number of output pixels in the given outputimage frame and the number of positions)). The given input image frame504 is shown to be divided into 12 groups 506, 507, 508, 509, 510, 511,512, 513, 514, 515, 516 and 517 of neighbouring input pixels, whereineach group comprises nine input pixels (as number of positions is equalto nine). The groups 516 and 517 of the neighbouring input pixels belongto the first input region 504A, and the groups 506-515 of theneighbouring input pixels belong to the second input region 504B.

Let us consider, for example, that light emanating from a given pixel(from amongst the 12 pixels Z1-Z 12) is to be shifted to nine positionsP1, P2, P3, P4, P5, P6, P7, P8, and P9 (of FIG. 4B) in a shiftingsequence: P1, P2, P3, P4, P5, P6, P7, P8, P9 (as depicted in FIG. 4E).The nine positions P1, P2, P3, P4, P5, P6, P7, P8, and P9 correspond tonine instants of time T1, T2, T3, T4, T5, T6, T7, T8, and T9,respectively, during displaying of the given pixel. A given output valueof colour components of the given pixel in the given output image frame502 depends on these nine positions P1-P9 to which the given pixel is tobe shifted during display of the given output image frame. At least oneprocessor (not shown) is configured to process nine input image framesto generate nine output image frames, wherein one input image frame isprocessed to generate one output image frame corresponding to a specificposition from amongst the positions P1-P9. The group 516 is shown tocomprise nine input pixels An, Bn, Cn, Dn, En, Fn, Gn, Hn, and In,wherein value of ‘n’ is 1, 2, 3, 4, 5, 6, 7, 8, and 9 for the nine inputimage frames. As example, in a first input image frame, the group 516comprises the nine input pixels A1, B1, C1, D1, E1, F1, G1, H1, and in asecond input image frame, the group 516 comprises the nine input pixelsA2, B2, C2, D2, E2, F2, G2, H2, and I2; and so on.

The at least one processor is configured to generate, from a given inputpixel in the group 516 within the first input region 504A of the giveninput image frame, the pixel Z6 for the first output region 502A of thegiven output image frame. In an example, the input pixel A1 of the firstinput image frame, the input pixel B2 of the second input image frame,input pixel C3 of a third input image frame, input pixel D4 of a fourthinput image frame, input pixel E5 of a fifth input image frame, inputpixel F6 of a sixth input image frame, input pixel G7 of a seventh inputimage frame, input pixel H8 of a eighth input image frame, and inputpixel 19 of a ninth input image frame are used to generate the pixel Z6of a first output image frame, a second output image frame, a thirdoutput image frame, a fourth output image frame, a fifth output imageframe, a sixth output image frame, a seventh output image frame, aneighth output image frame, and a ninth output image frame, correspondingto the instants of time T1, T2, T3, T4, T5, T6, T7, T8, and T9,respectively. Notably, all pixels in the first output region 502A of thenth output image frame 502 are generated in a similar way. In anexample, the pixel Z7 is also generated in a similar manner as the pixelZ6.

Moreover, the at least one processor is configured to combine nine inputpixels in the group 506 within the second input region 504B of the giveninput image frame 504 to generate the pixel Z1 for the second outputregion 502B of the given output image frame 502. Referring to the aboveexample, a combination of nine input pixels of the group 506 of thefirst input image frame, the second input image frame, the third inputimage frame, the fourth input image frame, the fifth input image frame,the sixth input image frame, the seventh input image frame, the eighthinput image frame, and the ninth input image frame, is used to generatethe pixel Z1 of the first output image frame, the second output imageframe, the third output image frame, the fourth output image frame, thefifth output image frame, the sixth output image frame, the seventhoutput image frame, the eighth output image frame, and the ninth outputimage frame, corresponding to the instants of time T1, T2, T3, T4, T5,T6, T7, T8, and T9, respectively. Notably, all pixels in the secondoutput region 502A of the nth output image frame 502 are generated in asimilar way. In an example, the pixels Z2, Z3, Z4, Z5, Z8, Z9, Z10, Z11,and Z12 are also generated in a similar manner as the pixel Z1.

Referring to FIG. 6 illustrated are steps of a method of displaying viaa display apparatus, in accordance with an embodiment of the presentdisclosure. The display apparatus comprises gaze-tracking means, animage renderer per eye, and a liquid-crystal device comprising aliquid-crystal structure and a control circuit, wherein theliquid-crystal structure is arranged in front of an image-renderingsurface of the image renderer. At step 602, the liquid-crystal structureis electrically controlled, via the control circuit, to shift lightemanating from a given pixel of the image renderer to a plurality ofpositions in a sequential and repeated manner, the given pixelcomprising at least one colour component. At step 604, gaze-trackingdata, collected by the gaze-tracking means, is processed to determine agaze direction of a user's eye. At step 606, a gaze point is determinedon an image plane of the image-rendering surface at which the user isgazing, based on the gaze direction of the user's eye. At step 608, afirst output image frame is displayed via the image renderer. At step610, it is detected whether or not a magnitude of a difference between afirst output value of a given colour component of the given pixel in thefirst output image frame and an initial second output value of the givencolour component of the given pixel in a second output image frameexceeds a first threshold difference, wherein the second output imageframe is to be displayed subsequent to the first output image frame.When it is detected that the magnitude of the difference between thefirst output value and the initial second output value exceeds the firstthreshold difference, at step 612, the initial second value in thesecond output image frame is updated to a sum of the first output valueand a product of a distance factor and a difference between the initialsecond output value and the first output value, wherein the distancefactor is a function of a distance of the given pixel from the gazepoint on the image plane. Otherwise, when it is detected that themagnitude of the difference between the first output value and theinitial second output value does not exceed the first thresholddifference, at step 614, the initial second value in the second outputimage frame is not updated, and this non-updated initial second value isused in the second output image frame. At step 616, the second outputimage frame is displayed via the image renderer.

The steps 602, 604, 606, 608, 610, 612, 614, and 616 are onlyillustrative and other alternatives can also be provided where one ormore steps are added, one or more steps are removed, or one or moresteps are provided in a different sequence without departing from thescope of the claims herein.

Modifications to embodiments of the present disclosure described in theforegoing are possible without departing from the scope of the presentdisclosure as defined by the accompanying claims. Expressions such as“including”, “comprising”, “incorporating”, “have”, “is” used todescribe and claim the present disclosure are intended to be construedin a non-exclusive manner, namely allowing for items, components orelements not explicitly described also to be present. Reference to thesingular is also to be construed to relate to the plural.

The invention claimed is:
 1. A display apparatus comprising:gaze-tracking means; an image renderer per eye; a liquid-crystal devicecomprising a liquid-crystal structure and a control circuit, wherein theliquid-crystal structure is arranged in front of an image-renderingsurface of the image renderer, wherein the liquid-crystal structure isto be electrically controlled, via the control circuit, to shift lightemanating from a given pixel of the image renderer to a plurality ofpositions in a sequential and repeated manner, the given pixelcomprising at least one colour component; and at least one processorconfigured to: process gaze-tracking data, collected by thegaze-tracking means, to determine a gaze direction of a user's eye;determine, based on the gaze direction of the user's eye, a gaze pointon an image plane of the image-rendering surface at which the user isgazing; display a first output image frame via the image renderer;detect whether or not a magnitude of a difference between a first outputvalue of a given colour component of the given pixel in the first outputimage frame and an initial second output value of the given colourcomponent of the given pixel in a second output image frame exceeds afirst threshold difference, wherein the second output image frame is tobe displayed subsequent to the first output image frame; when it isdetected that the magnitude of the difference between the first outputvalue and the initial second output value exceeds the first thresholddifference, update the initial second output value in the second outputimage frame to a sum of the first output value and a product of adistance factor and a difference between the initial second output valueand the first output value, wherein the distance factor is a function ofa distance of the given pixel from the gaze point on the image plane;and display the second output image frame via the image renderer.
 2. Thedisplay apparatus of claim 1, wherein the distance factor decreases withan increase in the distance.
 3. The display apparatus claim 1, whereinthe distance is measured in degrees as an angular distance between thegiven pixel and the gaze point, wherein the distance factor has a valuethat lies in a range of 1-5 for the angular distance that lies in arange of 0-30 degrees.
 4. The display apparatus of claim 1, wherein thedistance is measured in pixels, wherein the distance factor has a valuethat lies in a range of 1-5 for the distance that lies in a range of1-1800 pixels.
 5. The display apparatus of claim 1, wherein differentdistance factors are to be employed for different colour components ofthe given pixel.
 6. The display apparatus of claim 1, wherein the atleast one processor is configured to: quantize the initial second outputvalue of the given colour component of the given pixel by dividing theinitial second output value with a quantization factor, to generate anintermediate second output value of the given colour component; and adda given noise-signal value to the intermediate second output value togenerate a given output value of the given colour component.
 7. Thedisplay apparatus of claim 6, wherein the at least one processor isconfigured to determine the given noise-signal value using a noisegenerator function or a noise texture lookup, based on pixel coordinatesof the given pixel.
 8. The display apparatus of claim 1, wherein the atleast one processor is configured to process an input sequence of inputimage frames to generate an output sequence of output image frames,wherein a number of input image frames in the input sequence and anumber of output image frames in the output sequence are equal to anumber of positions in the plurality of positions, and wherein a numberof pixels in a given input image frame is equal to a product of a numberof pixels in a given output image frame and the number of positions,wherein, when generating the output image frames, the at least oneprocessor is configured to: determine, based on the gaze point on theimage plane at least a first input region and a second input regionwithin each input image frame, wherein the first input region includesand surrounds the gaze point, and the second input region surrounds thefirst input region; divide each input image frame into a plurality ofgroups of neighbouring input pixels based on a shifting sequence inwhich the light emanating from the given pixel is to be shifted to theplurality of positions, wherein a number of input pixels in a givengroup of neighbouring input pixels is equal to the number of positionsin the plurality of positions; and generate, from an N^(th) input pixelin a given group of neighbouring input pixels within a first inputregion of an N^(th) input image frame in the input sequence, acorresponding pixel for a first output region of an N^(th) output imageframe in the output sequence.
 9. The display apparatus of claim 8,wherein, when generating the output image frames, the at least oneprocessor is configured to combine input pixels in a given group ofneighbouring input pixels within a second input region of an M^(th)input image frame in the input sequence to generate a correspondingpixel for a second output region of an M^(th) output image frame in theoutput sequence.
 10. The display apparatus of claim 8, wherein the firstoutput value of the given colour component of the given pixel in thefirst output image frame is generated from an input value of the givencolour component of a first input pixel in a given group of neighbouringinput pixels in a first input image frame, wherein the at least oneprocessor is configured to: detect whether or not an initial differencebetween the input value of the given colour component of the first inputpixel and an input value of the given colour component of a second inputpixel in the given group of neighbouring input pixels in the first inputimage frame lies within a second threshold value from the differencebetween the first output value and the initial second output value; andwhen it is detected that the initial difference lies within the secondthreshold value from the difference between the first output value andthe initial second output value, employ the initial second output valueof the given colour component of the given pixel in the second outputimage frame, irrespective of whether or not the magnitude of thedifference between the first output value and the initial second outputvalue exceeds the first threshold difference.
 11. A method ofdisplaying, via a display apparatus comprising gaze-tracking means, animage renderer per eye, and a liquid-crystal device comprising a liquidcrystal structure and a control circuit, wherein the liquid-crystalstructure is arranged in front of an image-rendering surface of theimage renderer, the method comprising: electrically controlling theliquid-crystal structure, via the control circuit, to shift lightemanating from a given pixel of the image renderer to a plurality ofpositions in a sequential and repeated manner, the given pixelcomprising at least one colour component; processing gaze-tracking data,collected by the gaze-tracking means, to determine a gaze direction of auser's eye; determining, based on the gaze direction of the user's eye,a gaze point on an image plane of the image-rendering surface at whichthe user is gazing; displaying a first output image frame via the imagerenderer; detecting whether or not a magnitude of a difference between afirst output value of a given colour component of the given pixel in thefirst output image frame and an initial second output value of the givencolour component of the given pixel in a second output image frameexceeds a first threshold difference, wherein the second output imageframe is to be displayed subsequent to the first output image frame;when it is detected that the magnitude of the difference between thefirst output value and the initial second output value exceeds the firstthreshold difference, updating the initial second output value in thesecond output image frame to a sum of the first output value and aproduct of a distance factor and a difference between the initial secondoutput value and the first output value, wherein the distance factor isa function of a distance of the given pixel from the gaze point on theimage plane; and displaying the second output image frame via the imagerenderer.
 12. The method of claim 11, wherein the distance factordecreases with an increase in the distance.
 13. The method of claim 11,wherein the distance is measured in degrees as an angular distancebetween the given pixel and the gaze point, wherein the distance factorhas a value that lies in a range of 1-5 for the angular distance thatlies in a range of 0-30 degrees.
 14. The method of claim 11, wherein thedistance is measured in pixels, wherein the distance factor has a valuethat lies in a range of 1-5 for the distance that lies in a range of1-1800 pixels.
 15. The method of claim 11, wherein different distancefactors are employed for different colour components of the given pixel.16. The method of claim 11, further comprising: quantizing the initialsecond output value of the given colour component of the given pixel bydividing the initial second output value with a quantization factor, togenerate an intermediate second output value of the given colourcomponent; and adding a given noise-signal value to the intermediatesecond output value to generate a given output value of the given colourcomponent.
 17. The method of claim 16, further comprising determiningthe given noise-signal value using a noise generator function or a noisetexture lookup, based on pixel coordinates of the given pixel.
 18. Themethod of claim 11, further comprising processing an input sequence ofinput image frames to generate an output sequence of output imageframes, wherein a number of input image frames in the input sequence anda number of output image frames in the output sequence are equal to anumber of positions in the plurality of positions, and wherein a numberof pixels in a given input image frame is equal to a product of a numberof pixels in a given output image frame and the number of positions,wherein the step of generating the output image frames comprises:determining, based on the gaze point on the image plane, at least afirst input region and a second input region within each input imageframe, wherein the first input region includes and surrounds the gazepoint, and the second input region surrounds the first input region;dividing each input image frame into a plurality of groups ofneighbouring input pixels based on a shifting sequence in which thelight emanating from the given pixel is to be shifted to the pluralityof positions, wherein a number of input pixels in a given group ofneighbouring input pixels is equal to the number of positions in theplurality of positions; and generating, from an N^(th) input pixel in agiven group of neighbouring input pixels within a first input region ofan N^(th) input image frame in the input sequence, a corresponding pixelfor a first output region of an N^(th) output image frame in the outputsequence.
 19. The method of claim 18, wherein the step of generating theoutput image frames further comprises combining input pixels in a givengroup of neighbouring input pixels within a second input region of anM^(th) input image frame in the input sequence to generate acorresponding pixel for a second output region of an M^(th) output imageframe in the output sequence.
 20. The method of claim 18, wherein thefirst output value of the given colour component of the given pixel inthe first output image frame is generated from an input value of thegiven colour component of a first input pixel in a given group ofneighbouring input pixels in a first input image frame, the methodfurther comprising: detecting whether or not an initial differencebetween the input value of the given colour component of the first inputpixel and an input value of the given colour component of a second inputpixel in the given group of neighbouring input pixels in the first inputimage frame lies within a second threshold value from the differencebetween the first output value and the initial second output value; andwhen it is detected that the initial difference lies within the secondthreshold value from the difference between the first output value andthe initial second output value, employing the initial second outputvalue of the given colour component of the given pixel in the secondoutput image frame, irrespective of whether or not the magnitude of thedifference between the first output value and the initial second outputvalue exceeds the first threshold difference.